WIP: ps2 bus driver

system/kernel/process.zig

@@ -162,6 +162,7 @@ fn system_call(state: *architecture.CpuState) void {
         .msi_bind => systemMsiBind(state),
         .io_read => systemIoRead(state),
         .io_write => systemIoWrite(state),
+        .clock => systemClock(state),
         _ => fail(state),
     }
 }
@@ -316,6 +317,15 @@ fn systemIoWrite(state: *architecture.CpuState) void {
     architecture.setSystemCallResult(state, 0);
 }
 
+/// clock() -> nanoseconds since boot: a monotonic time source. The kernel already owns
+/// the scheduling timer and computes this for preemption, so surfacing it is pure
+/// mechanism — no policy (wall-clock time, calendars, timezones are a user-space
+/// service layered on top). It lets a driver bound a poll loop by real time instead of
+/// a spin count, and time short delays.
+fn systemClock(state: *architecture.CpuState) void {
+    architecture.setSystemCallResult(state, architecture.nanos());
+}
+
 /// dma_alloc(len, flags) -> vaddr (rax), paddr (rdx): grant `len` bytes (rounded up to
 /// whole pages) of DMA-capable memory — physically contiguous, zeroed, pinned, and
 /// strong-uncacheable (coherent) — mapping it into the caller's DMA arena and handing